Scanning SQUID Platform
selected customer applications
A scanning-SQUID microscope is an ultra-sensitive system for quantitative measurement of weak local magnetic fields on the microscale.
The probe consists of a superconducting quantum interference device
(SQUID), which is scanned several hundreds of nanometers above the
sample surface.
The biggest advantage of sSQUIDs over other magnetic scanning probe
techniques is its unmatched magnetic field sensitivity down to the nT
range [1]. The drawback on the other hand is the limited spatial resolution
of usually above 1 µm only, although there are some promising new approaches with much higher spatial resolution [2].
Collaborating with the group of K. Moler & J. Kirtley (Stanford, USA), attocube has designed a platform for cryogenic sSQUID, based on the
attoSHPM. The microscope includes all necessary scanner, positioners,
cabling, electronics and a sensor head with an adjustable tilt stage for the
sensor, but no SQUID sensor or SQUID electronics. It provides a low temperature lateral scan range of 125 μm, which can optionally be equipped
with encoders for closed loop operation and fully linearized scans.
If needed, a specially adapted microscope configuration allows for large
temperature gradients of up to 100 K (liquid cryostat) between SQUID
sensor (kept at less than 7 K) and the sample [3].
This allows to study temperature dependent effects and samples with
high transition temperatures despite using a sensitive superconducting
device.
50 µm
Internal magnetic fields in natural sands
In this application, samples of natural sand were investigated with a cryogenic sSQUID as described above. The measurements indicate large internal magnetic field variations over tens of microns with up to 2 mT, as well
as variations in excess of 50 µT over smaller ranges. These findings clearly
show that unaccounted internal fields can significantly alter NMR data in
unknown samples [4].
[1] M. Zech et al., Microscopy Today 19 (06), 34-38 (2011)
[2] A. Finkler et al., Rev. Sci. Inst. 83, 073702 (2012)
[3] B. Kalisky et al., Nature Materials 12, 1091 (2013)
[4] J.O. Walbrecker, B. Kalisky, D. Grombacher, J. Kirtley, K.A. Moler and R. Knight, Journal of
Magnetic Resonance 242, 10–17 (2014)
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